The invention relates to an automated cruise control system in a vehicle.
Cruise control systems have been developed for a wide variety of vehicles and have evolved to include a variety of features. Typical cruise control systems function by applying engine power to maintain a vehicle""s speed at a driver-selected set speed, relieving the driver from manually adjusting the vehicle""s speed. Additionally, a cruise control system may have additional functions to accelerate while cruising or resume the cruise set speed after braking.
However, a problem can develop with typical cruise control systems when the vehicle encounters hilly terrain with steep undulating grades. For example, as the vehicle ascends a steep grade before cresting a hill, the vehicle""s speed might lag behind the cruise set speed. Subsequently, the vehicle begins descending the grade on the other side of the crest, and the vehicle begins to accelerate due to gravity. Nevertheless, the cruise control system maintains engine power in an attempt to reach the cruise set speed, and the vehicle unnecessarily expends fuel. Further, the vehicle typically overshoots the cruise set speed, so the driver must brake. As a result, under these conditions, traditional cruise control systems waste fuel and increase brake wear.
To reduce costs associated with traditional cruise control system inefficiency, an organization may institute a training program advising drivers to either suspend cruise control operation or adjust the cruise set speed under certain specified conditions. However, drivers may fail to so act because they face a variety of other tasks when driving. In addition, an inexperienced driver may fail to suspend the cruise control system because the driver simply does not assess terrain conditions properly. Finally, the training program itself requires costs possibly outweighing any savings gained.
The invention provides a system and related methods for monitoring terrain grades encountered by a vehicle. Upon determining the vehicle has encountered a particular type of terrain, the system performs a terrain adaptive action. For example, the system provides an alert to a driver (e.g., a driver message) or modifies a vehicle system (e.g., the cruise control system).
In one embodiment, the system generates an alert when the system determines the vehicle is cresting a hill. First, the system determines if the vehicle has climbed a substantial grade as indicated by significant increase in elevation and lag behind the cruise set speed. Then, after the system detects a sustained increase in the rate of the vehicle""s acceleration for a substantial period, the system determines the vehicle is cresting the hill. The system then provides the alert to the driver (e.g., in the form of a driver message), advising reduction of the cruise set speed.
In another embodiment, the system automatically modifies the cruise set speed without driver intervention. The driver can subsequently reset (i.e., resume) the cruise set speed by pressing a resume switch.
In yet another embodiment, the system automatically sets the cruise set speed to the current speed without driver intervention; subsequently, the set speed is automatically upwardly adjusted as the vehicle accelerates. The set speed is capped at its original value.
The system supports a fuzzy logic feature in which a degree of confidence value is maintained to indicate with what certainty the system has determined the vehicle is cresting a hill. The degree of confidence value is increased and decreased according to an increase-in-acceleration rule. Once the degree of confidence value reaches a target degree of confidence value, the system takes a terrain adaptive action.
Some of the illustrated implementations include various features to increase performance. For example, some of the parameters monitored by the system can be smoothed (e.g., with an averaging function) for more accurate analysis.
Several benefits result from the arrangement provided by the invention. Since a downward grade may follow the crest of a hill, the system can employ gravity to accelerate the vehicle rather than expending extra engine power. Thus, the system avoids unnecessarily expending fuel or overshooting the cruise set speed. As a result, the system increases fuel economy and avoids brake wear, reducing costs associated with vehicle operation and maintenance. Such benefits are particularly useful in the field of long-haul trucks.
Further advantages and features of the invention will become apparent with reference to the following detailed description and accompanying drawings.